Pectin, a food product used in the manufacture of jams, jellies, and other products that require gel-forming properties, has normally been made from apple pomace or citrus fruit peel. A desire to find other sources of pectin has led to research to find a method of producing pectin from sugar beets, a world-wide product that has not been successfully used as a valuable source of other food products, except for animal feed.
In Journal of American Chemistry and Science, Vol. 72 pp. 813-816 (February 1950) there is an article by Pippen et al. which points out that pectin from sugar beets has not exhibited the necessary jelling power to make it commercially attractive, and mentions various theories which have been proposed to explain this lack of jelling power. Among these theories are:
1. The presence on the pectin molecule of acetyl groups not found to the same extent on apple or citrus pectin; PA1 2. The low molecular weight of the beet pectin molecule as compared to the higher molecular weight of the apple and citrus pectin; and PA1 3. The presence of too many nonuronide groups on the beet pectin molecule as compared to the apple and citrus pectin. Pippen et al. concluded that beet pectin had an acceptable jelling power if the acetyl content of the pectin molecule was not greater than about 1% by weight. PA1 Maclay et al. U.S. Pat. No. 2,550,705; PA1 Cole U.S. Pat No. 2,577,232; PA1 Leo et al. U.S. Pat. No. 2,703,758; PA1 Leo et al. U.S. Pat. No. 2,801,178; and PA1 Wiles U.S. Pat. No. 3,622,559. PA1 Bishop U.S. Pat. No. 2,626,706; and PA1 Bishop U.S. Pat. No. 2,647,890. PA1 (a) mixing dry granular beet pulp with an aqueous solution of a strong, mineral acid, preferably hydrogen chloride, at about 45.degree. C. for about two days to produce a dry, free-flowing pulp mass having an acetyl content of not more than about 1%, by weight; PA1 (b) mixing one part of the pulp mass with about 10-20 parts of hot water, with rigorous agitation for about one hour at 60.degree.-70.degree. C.; PA1 (c) separating the resulting mixture into waste solids and a liquid containing pectin values; PA1 (d) stirring and cooling the liquid from step (c) to about 20.degree.-25.degree. C., adding aluminum chloride to obtain a pH drop of about 0.1 in a pH range of 1.8-2.25 and subsequently adding ammonium hydroxide until the pH is raised to about 4.0-4.5, while allowing solids to precipitate as an aluminum pectinate in a liquid medium; PA1 (e) separating the aluminum pectinate solids from the liquid medium to produce a first liquid waste stream; PA1 (f) mixing one part of the separated wet, aluminum pectinate solids with 2.5-3.0 parts of 95% alcohol acidified with HCl to a pH of about 2.0 and blending at high speed into a homogenized mixture of precipitated pectin in the liquid alcohol medium; PA1 (g) separating the pectin precipitated solids from the liquid alcohol medium, and recovering dry storable pectin powder; and PA1 (h) subjecting the liquid alcohol medium to distillation and recovery steps to recover the alcohol and the aluminum chloride for reuse. PA1 (a) milling dry sugar beet pulp to a particle size of about 2 mm; PA1 (b) mixing the milled pulp with about 5% by volume aqueous HCl at 45.degree. C. and leaving the mixture for about 48 hours at a solid-to-liquid weight ratio of about 1.0 to 2.5 to hydrolyze the pulp and remove acetyl groups; PA1 (c) vigorously stirring said pulp solids with hot water at a temperature of about 60.degree.-70.degree. C. for about one hour; PA1 (d) passing the resulting mixture over a screen to remove the liquid from waste solids; PA1 (e) mixing the liquid from the screen with bentonite or decalite and filtering the resulting mixture to remove substantially all solids and recover a polished, clear liquor containing dissolved pectin values; PA1 (f) cooling the liquor in a heat exchanger to about 20.degree.-25.degree. C.; PA1 (g) adding aluminum chloride to cause a pH drop of about 0.1 unit in a pH range of 1.8-2.25; PA1 (h) adding ammonium hydroxide to raise the pH to about 4.0-4.5; PA1 (i) allowing a precipitate of aluminum pectinate to form, separating the solids from the liquor in a helical conveyor centrifuge, and washing twice with cold water; PA1 (j) vigorously blending the centrifuged solids and sufficient acidified 95% alcohol at a pH of about 2.0 to produce a mixture of pectin containing solids and a liquid alcoholic medium of about 60% alcohol, and centrifuging to separate pectin solids from the alcoholic medium; PA1 (k) distilling the resultant alcoholic medium to recover 95% alcohol and an acidic aluminum-containing liquid; PA1 (l) subjecting the pectin-containing solids to washing and drying to produce dry pectin powder; PA1 (m) treating the aluminum-containing liquid with potassium hydroxide to raise the pH to about 4 to recover precipitated aluminum hydroxide by filtering, and adding hydrochloric acid to the precipitate to a pH of about 2.0-2.5 to solubilize aluminum chloride which then can be recovered as a liquid or a solid for recycling into step (g).
Generally, beet pectin has about 3-4% acetyl and 12-14% methoxyl content which is too high in acetyl content to provide good jelling power. The difficulty of preparing an acceptable beet pectin is that when acetyl groups are removed from the beet pectin molecule, methoxyl groups are also removed.
High methoxyl content, i.e., about 8-13% is necessary in order to provide jelling power for fruit juices and other acidic substances. Medium methoxyl content, i.e., 5-8% is needed for pectin to be used in nonacidic media, e.g., milk, to prepare puddings and the like. Low methoxyl content, i.e., 0-5% is not useful in jelling procedures. The largest use is in jelling fruit juices, and therefore, the most desirable pectin is one with high methoxyl content and low acetyl content. Acetyl content must be below about 1% in order not to interfere with the jelling power. The prior art has not known how to make such a pectin from beet pulp. The art of making pectin from citrus or apple peel is represented by:
The art relating to processes for making pectin from beets is found in:
Insofar as is known, the prior art has not known how to make a pectin from beet pulp which has a good jelling power and has a high-to-medium methoxyl content.
It is an object of this invention to provide an improved process for preparing acceptable pectin from beets. It is another object of this invention to provide a process for preparing beet pectin of low acetyl content and a high-to-medium methoxyl content. Still other objects will become apparent from the more detailed description which follows.